1. Field of the Invention
One embodiment of the disclosed invention relates to an electric double layer capacitor, a lithium ion capacitor, and a charging device.
2. Description of the Related Art
Solar energy has many advantages over an energy source which has been in the mainstream in recent years. For example, solar energy is virtually infinite and can be used all over the world.
Solar energy is effectively used in a variety of fields. In a building or a car, for example, a portion which is irradiated with sunlight is provided with a solar cell and the solar energy is converted into electricity by the solar cell. The electricity obtained in this manner can be used as part of lighting for a building or a power source for a car.
Solar energy can be obtained in daytime when sunlight can be obtained; however, if electricity obtained as the above is stored, the electricity can also be used at night time or at the time of rain when sunlight cannot be obtained. Accordingly, solar energy is an energy source with which valuable natural resources are not reduced and destroyed (see Patent Document 1).
As power storage systems (also referred to as a power storage device) which store electricity converted by a solar cell, a secondary battery, an electrochemical capacitor, or the like can be given.
As an electrochemical capacitor, a hybrid capacitor such as a lithium ion capacitor (see Patent Document 2), an electric double layer capacitor (EDLC) (see Patent Documents 3 and 4), and the like have been developed.